A typical subsea wellhead assembly has a high pressure wellhead housing supported in a lower pressure wellhead housing and secured to casing that extends into the well. One or more casing hangers land in the wellhead housing, the casing hanger being located at the upper end of a string of casing that extends into the well to a deeper depth. A string of tubing extends through the casing for production fluids.
Well components are pressure tested after installation to detect leaks. A plug comprising a seal can be used to pressure test the well components. The plug can be landed at a tubular well component and the seal can be set to establish a seal at the well component. The portion of the well below the plug can then be hydraulically pressurized from a remotely operated vehicle (“ROV”) or via a hydraulic line from the surface to thereby pressure test the well components below the plug. The plug is usually removed after testing of the well component but can remain in place until a later time when other components, such as a tree, are installed. The pressure tested well component can be, for example, a wellhead housing, a tree, a gooseneck connection, or a pigging head. Further, the integrity of riser components can also be pressure tested by setting the plug in the riser. One example of riser component to be pressure tested would be a gooseneck connection at the top of a freestanding riser.
The plug's seal is typically set using the plug's own weight. This weight-activated plug setting approach is adequate to set seals with a setting force of a few hundred pounds. However, plug seals used to conduct high pressure tests of well components can require setting forces of approximately 2,000 psi, depending on size. The weight of the plug is thus insufficient to set these high pressure seals that can be rated for test pressures of up to 15,000 psi.
One approach attempting to address the shortcomings of weight activated setting calls for the use of a tool or an ROV to set plugs with seals having a higher setting force. The tool or ROV can screw in a plug having a seal with up to a 5000 psi setting force. However, the force applied by an ROV may also be insufficient to set a seal assembly for a plug rated for test pressures of 15,000 psi or more.
A need exists for a technique that addresses the seal setting problems described above. In particular a need exists for a technique to set a high pressure plug seal for testing well components. The following technique may solve these problems.